docs: def keystone_configure_api_version(self, sentry_relation_pairs, deployment,
                                         api_version):
          """Configure preferred-api-version of keystone in deployment and
             monitor provided list of relation objects for propagation
             before returning to caller.
  
          :param sentry_relation_pairs: list of sentry, relation tuples used for
                                        monitoring propagation of relation data
          :param deployment: deployment to configure
          :param api_version: value preferred-api-version will be set to
          :returns: None if successful.  Raise on error.
          """
          self.log.debug("Setting keystone preferred-api-version: '{}'"
                         "".format(api_version))
  
          config = {'preferred-api-version': api_version}
          deployment.d.configure('keystone', config)
          deployment._auto_wait_for_status()
          self.keystone_wait_for_propagation(sentry_relation_pairs, api_version)